Nitrocellulose Composition And Uses Therefor

ABSTRACT

A nitrocellulose composition comprises an admixture comprising: from about 75 weight percent to about 85 weight percent nitrocellulose; and from about 15 weight percent to about 25 weight percent camphor, based upon the weight of the admixture; and from about 1 weight percent to about 5 weight percent of a stabilizer (based on the total weight of the composition), wherein the stabilizer is chosen from the group consisting of N,N-Diethyl-N,N′-diphenylurea, N,N′-Dimethyl-N,N′-diphenylurea, 1,1-Diphenylurea, N-methyl-N,N′-diphenylurea, 1-Ethyl-3,3′-diphenylurea, Diphenylamine, 2-Nitro-diphenylamine, 4-Nitro-diphenylamine; Triphenylamine; p-Nitro-N-methylaniline, p-Nitro-ethylaniline, soybean oil, castor oil, sodium silicate, lactic acid amide, and benzonate; and from about 1 weight percent to about 5 weight percent of azodicarbonic acid diamide, based on the total weight of the composition. The composition is heated at a temperature sufficient to cause it to polymerize, after which it is formed into sheets, from which components for munitions, such as artillery, small arms, modular artillery charge systems and mortar increments are formed. The components of the mortar increments are joined together, and after being filled with a propellant composition, one or more mortar increments is attached to a mortar shell.

FIELD OF THE INVENTION

Embodiments of the present invention are nitrocellulose compositions. These compositions can be used in a variety of artillery and small arms such as but not limited to caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, head charges, underwater charges and others. In one embodiment, the nitrocellulose composition can be used to prepare empty propellant containers, known as Mortar Increment Containers (“MICs”). The MICs are cellulose nitrate based containers into which a propellant mixture is placed, and one or more filled MICs are attached to a mortar shell.

BACKGROUND OF THE INVENTION

Nitrocellulose (also referred to as cellulose nitrate or gun cotton) has been used in the manufacture of various products, ranging from products as diverse as nail enamel, filters for laboratory or commercial use for sterilizing or purifying liquids, photographic film, to explosives such as gun powder, propellants, and/or containers to hold such explosives or propellants.

An example of a nitrocellulose-based product is a Mortar Increment Container (“MIC”). These are devices into which a propellant is placed, with one or more filled MICs being attached to a mortar shell. By increasing or decreasing the number of MICs attached to a mortar shell, the range of the mortar shell can be increased or decreased, respectively. MICs are produced in a number of sizes, to fit mortars having diameters of, for example only, and not intended as any limitation, 60 mm, 81 mm and 120 mm that are used by the military.

Several patents and published patent applications describe the structure of MICs, such as U.S. Pat. No. 7,059,251 B2 (Khanna et al.) and U.S. Pat. App. Pub. No. 2005/0268806 A1 (Harjula et al.).

Generally, MICs are manufactured from cellulose nitrate, as disclosed in Jordan et al (U.S. Pat. No. 4,898,097), and U.S. Pat. App. Pub. No. 2005/0268806 A1, a felted cellulose nitrate (Dryer et al., U.S. Pat. No. 7,024,998), or combustible felted fiber material (Wong et al., U.S. Pat. No. 7,025,000).

U.S. Pat. No. 5,218,166 (Schumacher) discloses a method of making a waterproof nitrocellulose based propellant composition, involving resolvating a nitrocellulose-based propellant with a solvent, adding glycerine and drying the resulting slurry. A mixture comprising nitrocellulose and camphor can be added to the resolvated mixture prior to drying. The method can be applied to a variety of artillery and small arms as well as in the aerospace and construction industry including but not limited to caseless munitions, mines, rocket motors, bag charges, mortar increments, head charges, underwater charges, plastic explosives and others.

In U.S. Pat. No. 6,645,325 B1 Nickel discloses using 3,6-dihydrazino-s-tetrazine as an additive to increase the burn rate of a nitrocellulose containing composition, describes problems associated with using nitrocellulose for smokeless powders, and that many agents used to increase the activity of nitrocellulose create additional disadvantages that the nitrocellulose was intended to overcome.

U.S. Pat. No. 3,711,343, to Dunigan et al. discloses the use of nitrocellulose sheets as a substitute for cloth powder bags. The nitrocellulose-based composition is a combustible material that may be formed in the shape of and serve as combustible cartridge cases or the like. The compositions use nitrocellulose base ball powder to which is added a plasticiser and an organic polyisocyanate. The compositions made using this invention can be formed or shaped by the use of appropriate molds.

In U.S. Pat. App. Pub. No. 2005/0268806 A1 Harjula et al. disclose an increment charge to be placed around a tail shaft of a fin-stabilized mortar projectile. The increment charge has a centrally located space for the tail shaft and a mounting opening in the space for mounting the increment charge. On the opposite side of the increment charge there is provided a protrusion that fits into the mounting opening of an adjacent increment charge for locking them in relation to each other. The increment charge may be manufactured by providing it with a casing made of a suitable inflammable material, such as nitrocellulose, and inserting gunpowder or other material suitable for the purpose into the casing.

U.S. Pat. No. 7,059,251 B2 (Khanna et al.) discloses a protecting charge support for a mortar cartridge for protecting mortar cartridges without the use of foam. The device is made of high density polyethylene or other resins, and sits over a plurality of mortar increments attached to the mortar tail tube. In U.S. Pat. No. 6,837,164 B1 they disclose protecting charge increment protectors made of polycarbonate/acrylonitrile butadiene styrene plastic.

In U.S. Pat. No. 7,025,000 Wong et al. disclose the structure of a propelling charge comprising a container made of a combustible felted fiber material, such as the four-increment M720A1 charge used for a 60 mm mortar.

U.S. Pat. No. 7,024,998 (Dryer et al.) discloses a projectile with a self-discarding or self-consumable propelling charge holder. The propelling charges may include a shell of felted nitrocellulose, filled with a suitable propellant composition. The propellant charge holder is an internal charge which initiates the reaction and combustion of the external charge increments, such that after the propelling charge increments have been consumed, and after the projectile has left the weapon, fins deploy from the projectile.

Jordan et al. (U.S. Pat. No. 4,898,097) disclose a modified propellant increment for training round use, in which mortar increment the body is composed of combustible propellant and has a plurality of holes defined through the body which communicate the exterior of the body with the hollow interior thereof. The body is composed of a combustible propellant material, such as a nitrocellulose.

In U.S. Pat. No. 4,326,901 Leneveu et al. disclose a process for coating nitrocellulose granules with polyvinyl nitrate in order to render the granules more easily compressible for making a fragmentable propellant.

Brown et al. (U.S. Pat. No. 5,811,726) disclose using azodicarbonamide in an explosive composition comprising 2-ethylhexyl nitrate and a granular solid oxidizer, such as ammonium nitrate, to reduce the sensitivity of the inventive binary explosive to achieve the most desirable properties for handling the inventive explosive as well as ease of detonation.

U.S. Pat. App. Pub. No. 2005/0092406 A1 (Fleming et al.) discloses the use of azodicarbonamide in an ammonium nitrate-based propellant, such as for vehicle air bag restraint devices, rockets or munitions, and which composition is essentially smoke-free according to one or more military standards and has an effective shelf life of 20 years or longer. The intended use of the compositions are in vehicular air bags.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a composition that can be readily combusted.

Another object of the present invention is to provide a composition that can be molded into a variety of shapes.

Still another object of the present invention is to provide a composition that can be used in a variety of artillery and small arms such as but not limited to caseless munitions, combustible cases, rocket motors, bag charges, modular artillery charge systems (“MACS”), mortar increments, head charges, underwater charges and others.

Still another object of the present invention is to provide a composition that can be formed into components of mortar increment containers.

Yet an object of the present invention is to provide a method for manufacturing a combustible composition.

Another object of the present invention is to provide a method for manufacturing a composition that can be molded into a variety of shapes.

Still another object of the present invention is to provide a method for manufacturing a composition that can be used in a variety of artillery and small arms such as but not limited to caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, MACS, head charges, underwater charges and others.

Yet another object of the present invention is to provide a method for manufacturing a composition that can be formed into components of mortar increment containers.

An embodiment of the composition comprises a mixture of about 80 percent (by weight of the composition) nitrocellulose, about 20 percent (by weight of the composition) camphor, about 2 percent (by weight of the composition) of a stabilizer, such as 1,1-diphenylurea; and about 3 percent (by weight of the composition) azodicarbonic acid diamide. The reagents are blended together, and formed into sheets which are used to manufacture the halves for the empty MICs. The thickness of the sheets range from 0.20 mm to 0.60 mm, and the halves are ultrasonically welded together to form the empty MICs. The empty MICs can then be filled with a propellant composition for use with an appropriate weapons system.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a plan view of a mortar increment container embodiment.

FIG. 2 is a side view of the embodiment shown in FIG. 1.

FIG. 3. illustrates a mortar shell to which several mortar increment containers have been attached.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention relate to nitrocellulose compositions that can be used in conjunction with explosives and weapons systems. Although embodiments of the present invention can be used in a variety of artillery and small arms, as well as in the aerospace and construction industries, including, but not limited to caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, modular artillery charge systems (“MACS”:), head charges, underwater charges and others. Embodiments of the composition could also be used for vehicular air bags and for seat-belt tighteners. One example is a nitrocellulose composition suitable for the manufacture of Mortar Increment Containers and other combustible materials. The MICs are generally produced in a number of sizes, to fit mortars having diameters of 60 mm, 81 mm and 120 mm that are used by the military.

Referring to FIG. 1, mortar increment container 10 is an arcuate container having two halves 12, 14 that are joined together to form a seam 16 and may include one or more openings 18 within the halves. Each half 12, 14 of MIC 10 is formed with a groove 20 that extends for part of the width of the MIC half. Multiple MICs can be stacked together along the length of a mortar shell 30 (FIG. 3). After the MIC has been manufactured, it can be filled with a propellant mixture (not shown) prior to its installation on a mortar shell, and the opening closed with an appropriate material.

The grooves 20 enable the MICs 10 to withstand stresses when the MICs 10 are mounted onto or taken off of the mortar shell 30, avoiding deformation of the surface of the MIC and loosening of the closing disc 22 after the MIC has been filled with propellant. Closing disc 22 comprises a disc body 24 with a diameter that is greater than the diameter of the filling hole 18. The closing disc 22 is attached to the MIC by means of an adhesive. The closing disc 22 can be manufactured from the same nitrocellulose composition as are the MICs 10, or other appropriate material.

The mortar shell 30 comprises a tail section 32 connected by a shaft 34 to the body 36. The body 36 includes a fuze (not shown).and the war head 38. The MICs 10 are designed to be mounted along the length of the tail 32. An ignition cartridge (not shown) is used to ignite the filled MIC 10, and the ignition cartridge is placed within the tail 32 and shaft 34 of the mortar shell 30.

Depending upon the supplier, and the intended use of the composition, nitrocellulose preparations are available with several different degrees of nitration (nitrogen content), ranging from about 10.7% to about 12.2%. Exemplary nitrocellulose compositions, such as those distributed by Nobel Enterprises, are graded as low nitrogen, mediun nitrogen and high nitrogen, having nitrogen contents of 10.7%-11.2%; 11.2%-11.7%; and 11.7%-12.2%, respectively. Nitrocellulose from other manufacturers may differ slightly from that described, such as a high nitrogen content of from 11.8%-12.3%, and depending upon the laws of the country of manufacture, the maximum permissible nitrogen content of nitrocellulose may vary from 12.2% to 12.6%. In one embodiment of the present invention, the nitrocellulose used has a nitration ranging from 11.0% to 11.4% (nitration of 11.2±0.2%).

The nitrocellulose is mixed with another agent such as a plasticizer. One example of a plasticizer is camphor. In embodiments of the present invention, nitrocellulose can be used at a concentration ranging from about 72% to about 84% by weight of the nitrocellulose-plasticizer mixture, and with a camphor concentration ranging from about 14% to about 20% by weight of the nitrocellulose-plasticizer mixture. Embodiments of the mixture could be made without camphor by using another plasticizer for the appropriate camphor concentration. In certain embodiments of the present invention, a mixture of about 80% nitrocellulose and about 20% camphor was prepared, prior to being mixed with the remaining components of the composition.

Examples of agents other than camphor that could be used as a plasticizer for the nitrocellulose composition of the present invention include liquid and/or solid plasticizer compounds, such as oxidant-type, for example, agents having active oxidizing groups, such as nitro, nitrate, nitroso and nitrite groups, such as pentaerythritol trinitrate, nitroglycerine diethylene glycol dinitrate, 1,2,4-trinitro-butane.

One or more stabilizers can be added to the nitrocellulose-plasticizer mixture. The stabilizers are generally added to give a final concentration ranging from about 0.5% by weight to about 10% by weight of the composition. In some embodiments the stabilizer is added to give a final concentration ranging from about 1.0% by weight to about 5% by weight of the composition, and in other embodiments added to give a final concentration ranging from about 1.5% by weight to about 4% by weight of the composition. Among the stabilizers that could be used are Centralites, such as, N,N-Diethyl-N,N′-diphenylurea and N,N′-Dimethyl-N,N′-diphenylurea (known as Centralite I and Centralite II, respectively). Akardites such as 1,1-Diphenylurea, N-methyl-N,N′-diphenylurea, or 1-Ethyl-3,3′-diphenylurea, known as Akardite I, Akardite II and Akardite III, respectively could be employed. Examples of modified amines are Diphenylamine, 2-Nitro-diphenylamine, 4-Nitro-diphenylamine; and Triphenylamine; exemplary modified anilines include p-Nitro-N-methylaniline or p-Nitro-N-ethylaniline. Oils such as soybean oil and castor oil, agents such as sodium silicate, lactic acid amide, and benzonate could be used as stabilizers. In embodiments of the present invention, the stabilizer used is N-methyl-N,N′-diphenylurea (Akardite II)

Azodicarbonic acid diamide is available in a variety of particle sizes from its' manufacturers (e.g., Lanxess Deutschland GmbH, Leverkusen-Bayerwerk Germany, under the trademark POROFOR®), ranging from 2.5 to 20 μm. In embodiments of the present invention, azodicarbonic acid diamide preparations having a particle size range of 2.6 μm to 3.4 μm (3.0±0.4 μm), or a range of 14.7 μm to 15.1 μm (14.9±2 μm) were used in the composition.

Without being bound to any particular theory, it is believed that because the azodicarbonic acid diamide is known as an exothermic blowing agent in the plastics industry, when the MIC composition containing it is rapidly heated when the weapon is fired, the azodicarbonic acid diamide expands, affecting the surface of the MICs by enlarging the area of the MIC that has been ignited, resulting in an enhanced burning of the MIC that has the effect of either a reduced residue or no residue of the MIC being left in the weapon.

The reagents are blended together, and using methods known to those skilled in the art, are formed into blocks by heating at a temperature that less than 100 degrees C., for a specified time period, during which time polymerization occurs. For some embodiments, the blocks arc formed by heating at a temperature of about 90 degrees C. for a time period ranging from about 8 hours to about 24 hours; in other embodiments, the time period may be about 16 hours or less, depending upon the size of the block being prepared. The blocks may range from about 50 kg to about 100 kg.

The polymerized blocks are then cut into sheets which are used to manufacture the components, (which are generally halves, and the closure discs) for the empty MICs. The thickness of the sheets could range from about 0.10 mm to about 1.00 mm, and in one embodiment the sheets are formed with thicknesses ranging from about 0.20 mm to about 0.60 mm. The sheets are processed by drawing, and cutting out the respective halves for the MICs. The components are then joined together to form the empty MICs. The methods for joining the MIC components together include adhesives, heating, ultrasonically welding, or other methods known to those skilled in the art. In the examples described below, the components are ultrasonically welded together to form the empty MICs, followed by beading of the welded edges.

Depending upon the combination of the MIC and the propellant contained in it, as well as the storage conditions, it is estimated that the MICs have a shelf-life of approximately twenty years. However, the shelf life can be affected if there is migration of reagents from the propellant powders contained in the MIC, such as the nitroglycerine contained in double- or triple-based powders.

The nitrocellulose composition could be prepared using a hot extrusion process, in which the nitrocellulose mixture is passed through a heated tube under pressure, during which time the nitrocellulose polymerizes. Alternatively, the admixture could be extruded through a heated nozzle, resulting in a rapidly polymerized product. Under such conditions, the nozzle could be heated to a temperature ranging from about 90 degrees C. to about 130 degrees C., where polymerization occurs within a matter of seconds. After the nitrocellulose mixture has been extruded, the polymerized material is sized and shaped as required by the final end product being made.

The methods of nitrocellulose manufacturing described herein can be applied to a variety of artillery and small arms as well as in the aerospace and construction industry including but not limited to caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, modular artillery charge systems, head charges, underwater charges, propellants for vehicular air bags or seat-belt tighteners, and others.

Therefore, although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of illustration and that numerous changes in the details of construction and arrangement of parts may be resorted to without departing from the spirit and scope of the invention. 

1. A nitrocellulose composition, the composition comprising an admixture comprising: from about 75 weight percent to about 85 weight percent nitrocellulose (based upon the weight of the admixture); and from about 15 weight percent to about 25 weight percent camphor, (based upon the weight of the admixture); and from about 1 weight percent to about 5 weight percent of a stabilizer (based on the total weight of the composition), wherein the stabilizer is chosen from the group consisting of N,N-Diethyl-N,N′-diphenylurea, N,N′-Dimethyl-N,N′-diphenylurea, 1,1-Diphenylurea, N-methyl-N,N′-diphenylurea, 1-Ethyl-3,3′-diphenylurea, Diphenylamine, 2-Nitro-diphenylamine, 4-Nitro-diphenylamine; Triphenylamine; p-Nitro-N-methylaniline, p-Nitro-N-ethylaniline, soybean oil, castor oil, sodium silicate, lactic acid amide, and benzonate; and from about 1 weight percent to about 5 weight percent of azodicarbonic acid diamide, based on the total weight of the composition.
 2. The nitrocellulose composition as described in claim 1, wherein the composition is heated to a temperature that is less than 100 degrees C., for a time period sufficient to polymerize the composition.
 3. The nitrocellulose composition as described in claim 2, wherein the polymerized composition is formed into a shape suitable for artillery munitions, small arms munitions, caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, modular artillery charge systems, head charges and underwater charges.
 4. The nitrocellulose composition as described in claim 3, wherein the polymerized composition is formed into a shape suitable for components of mortar increment containers (“MICs”).
 5. The nitrocellulose composition as described in claim 2, wherein the admixture comprises from about 78% to about 82% nitrocellulose and from about 18% to about 22% camphor, based on the total weight of the composition.
 6. The nitrocellulose composition as described in claim 2, wherein the composition comprises from about 1% to about 3% azodicarbonic acid diamine, based on the total weight of the composition.
 7. The nitrocellulose composition as described in claim 5, wherein the composition comprises from about 1% to about 3% 1,1-Diphenylurea (based on the total weight of the composition).
 8. The nitrocellulose composition as described in claim 5, wherein the nitrocellulose is characterized by having a nitration of about 11.0% to about 11.4%.
 9. A method of manufacturing a composition, the method comprising the steps of: forming an admixture comprising from about 75 weight percent to about 85 weight percent nitrocellulose (based on the weight of the admixture); and from about 15 weight percent to about 25 weight percent camphor (based on the weight of the admixture); adding from about 1 weight percent to about 5 weight percent of a stabilizer (based on the total weight of the composition), wherein the stabilizer is chosen from the group consisting of N,N-Diethyl-N,N′-diphenylurea, N,N′-Dimethyl-N,N′-diphenyl urea, 1,1-Diphenylurea, N-methyl-N,N′-diphenylurea, 1-Ethyl-3,3′-diphenylurea, Diphenylamine, 2-Nitro-diphenylamine, 4-Nitro-diphenylamine; Triphenylamine; p-Nitro-N-methylaniline, p-Nitro-N-ethylaniline, soybean oil, castor oil, sodium silicate, lactic acid amide, and benzonate; and mixing about 1 weight percent to about 5 weight percent of azodicarbonic acid diamide (based on the total weight of the composition); and heating the mixture to a temperature sufficient to polymerize the composition.
 10. The method as described in claim 9, wherein the mixture is heated to a temperature less than 100 degrees C.
 11. The method as described in claim 10, further comprising the step of forming the polymerized composition into a sheet, the sheet having a thickness ranging from about 0.10 mm to about 1.0 mm.
 12. The method as described in claim 10, further comprising the step of forming the polymerized composition into a sheet, the sheet having a thickness ranging from about 0.20 mm to about 0.60 mm.
 13. The method as described in claim 12, further comprising the step of forming the sheet into a shape suitable for a mortar increment container (“MIC”).
 14. The method as described in claim 13, further comprising the step of forming the sheet into at least two components for the MIC.
 15. The method as described in claim 14, further comprising the step of joining the components to form the MIC.
 16. The method as described in claim 15, wherein the step of joining comprises ultrasonic welding.
 17. The method as described in claim 9, wherein the nitrocellulose is characterized by having a nitration of about 11.0% to about 11.4%.
 18. The method as described in claim 9, wherein the composition comprises from about 1% to about 3% azodicarbonic acid diamide (based on the total weight of the composition)
 19. A nitrocellulose composition, the composition formed by a process comprising the steps of: forming an admixture comprising from about 75 weight percent to about 85 weight percent nitrocellulose (based on the weight of the admixture), from about 15 weight percent to about 25 weight percent camphor (based upon the weight of the admixture); adding about 1 weight percent to about 5 weight percent of a stabilizer (based on the total weight of the composition), wherein the stabilizer is chosen from the group consisting of N,N-Diethyl-N,N′-diphenylurea, N,N′-Dimethyl-N,N′-diphenylurea, 1,1-Diphenylurea, N-methyl-N,N′-diphenylurea, 1-Ethyl-3,3′-diphenylurea, Diphenylamine, 2-Nitro-diphenylamine, 4-Nitro-diphenylamine; Triphenylamine; p-Nitro-N-methylaniline, p-Nitro-N-ethylaniline, soybean oil, castor oil, sodium silicate, lactic acid amide, and benzonate; and mixing about 1 weight percent to about 5 weight percent of azodicarbonic acid diamide, (based on the total weight of the composition); and heating the mixture to a temperature of about 90 degrees C. to polymerize the composition.
 20. The nitrocellulose composition formed by the process as described in claim 19, wherein the process further comprises the step of placing the mixture into a mold prior to the heating step.
 21. The nitrocellulose composition formed by the process as described in claim 20, wherein the process further comprises forming the polymerized composition into a sheet, the sheet having a thickness ranging from about 0.10 mm to about 1.0 mm;
 22. The nitrocellulose composition formed by the process as described in claim 21, wherein the process further comprises forming the polymerized composition into a sheet, the sheet having a thickness ranging from about 0.20 mm to about 0.6 mm;
 23. The nitrocellulose composition formed by the process as described in claim 22, further comprising the step of forming the sheet into a shape suitable for artillery munitions, small arms munitions, caseless munitions, combustible cases, rocket motors, bag charges, mortar increments, modular artillery charge systems, head charges and underwater charges.
 24. The nitrocellulose composition formed by the process as described in claim 22, further comprising the step of forming the sheet into a shape suitable for components of mortar increment containers (“MICs”).
 25. The nitrocellulose composition formed by the process as described in claim 22, further comprising the step of forming the composition into a shape suitable for use in components of vehicular air bag systems and vehicular seat-belt tensioning systems. 